Juan Battle and Earl Wright II published W. E. B. Du Bois's Talented Tenth: A Quantitative Assessment in the Journal of Black Studies, 32:6 (2002):654-672. It can be downloaded from Dr. Wright's web site as a PDF file.
In the United States, the size of parking spaces varies. Typically they fall between 7.5 to 9 feet wide and 10 to 20 feet long. The most common size is 8.5 feet wide by 19 feet long.
They may vary from 8' x 18' to 10' x 20' in general. The MUTCD (Manual on Uniform traffic control devices) which is the national wide standard states the a parking space minimum is 8'x22' and 8'x20' for compact vehicles except on the ends. The end spaces in a line may be as short as 18'.